Carboxyl-containing acrylate copolymer and epoxy resin

ABSTRACT

A coating agent comprises a binding agentcontaining at least one acrylate copolymer (A) with carboxyl groups and/or at least one acrylate copolymer (B) with epoxide groups, the acrylate copolymers (A) and (B) being obtained by solution polymerization using less than 5% by weight based on the total weight of monomers of one or more polysiloxane macromonomers a 1  having a number-average molecular weight of 1000 to 40,000 and on average 0.5 to 2.5 ethylenically unsaturated double bonds per molecule; and one or more epoxy resins.

The present invention relates to coating agents which comprise, as thebinding agent, at least one polymer containing carboxyl groups and, asthe hardener, at least one epoxy resin having on average more than oneepoxide group per molecule.

The present invention furthermore relates to processes for thepreparation of these coating agents and to their use, and to processesfor coating substrates.

Very high quality requirements are imposed in particular on coatingagents which are employed in the field of automobile repair painting.Thus, these coating agents must be curable at low temperatures (≦100°C., preferably ≦80° C.) and at the same time already be dry to dust andtack-free after less than 7 hours. A good resistance to solvents,resistance to weathering, resistance to taping, resistance to yellowingand sandability, and a low intrinsic color of the resulting coatings arefurthermore required. It must be possible, furthermore, to paint overthe coatings, in order thus to guarantee that paint damage in theadjacent region and in the region of the repair paint can also berepaired.

Coating agents based on acrylate copolymers containing carboxyl groupsand on epoxy resins which are also used in the field of automobilerepair painting have been known for a long time and are described, forexample, in EP-B-51 275, EP-A-123793, DE-OS 26 35 177, JP-OS 76 338/77,WO 87/02041 and WO 89/08132. However, these known coating agents haveonly a low stability to weathering and a low surface slip, and as aresult a poor resistance of the resulting coatings to chemicals.Compatibility problems moreover occur between the acrylate copolymerscontaining carboxyl groups and some epoxy resins.

Coating agents for coating automobiles are furthermore known from EP-A358153, these comprising either a) a copolymer which is obtainable usingpolysiloxane macromonomers having at least two functional groups permolecule and vinyl monomers containing epoxide groups, or b) 1 mixtureof a polymer (1) based on polysiloxane macromonomers having at least twofunctional groups and a polymer (2) based on vinyl monomers containingepoxide groups. These coating agents furthermore contain an aluminumchelate compound and/or a titanium chelate compound and/or a zirconiumchelate compound as the hardener.

Since the functional groups of the polysiloxane macromonomers contributetoward crosslinking of the coating agents, a very high content of thispolysiloxane macromonomer in the copolymer is required to guaranteeadequate crosslinking. On the other hand, crosslinking of the coatingagents by a carboxy/epoxy reaction is not described in EP-A-358153.These moisture-hardening coating agents known from EP-A-358153furthermore have the disadvantage of a lower storage stability afterdrums have been opened and higher production costs of the coatingagents.

Moisture-hardening coating agents furthermore are known from DE-OS 38 39215, these comprising, as the binding agent, a resin which is obtainableby polymerization of a vinyl monomer containing alkoxysilane and/or apolysiloxane macromonomer with a vinyl monomer containing epoxide groupsin the presence of a resin containing carboxyl groups. These coatingagents in turn contain a chelate compound as the hardener.

A coating agent based on acrylate copolymers containing hydroxyl groupsand on polyisocyanates furthermore is known from JP-OS 2163177, thisbeing employed, in particular, as a house paint. The coatings here aredistinguished by an improved stability to weathering, which is achievedby copolymerization of 0.5 to 15% by weight of a polysiloxanemacromonomer into the acrylate copolymer containing hydroxyl groups. Itis also known from U.S. Pat. No. 4,754,014 that the weatheringresistance of coating agents based on acrylate copolymers containinghydroxyl groups can be improved by modification with polysiloxanemacromonomers. However, coating agents based on acrylate copolymerscontaining carboxyl groups and on epoxy resins are not described inJP-OS 2163177 and U.S. Pat. No. 4,754,014.

It is known from EP-B 175 092 that the flow properties and thefrictional properties and scratch resistance of coatings can be improvedby adding siloxanes, which are free from polyether groups and modifiedby polyester, to the coating agents. The use of polymerizable,ethylenically unsaturated polysiloxane macromonomers for themodification of binding agents based on acrylate copolymers is notdescribed in EP-B 175092.

Finally, coating agents based on epoxy-functional polymers and onpolymers containing carboxyl groups are known from EP-A-212 457, thesebeing particularly suitable for metallic multicoat painting. Both thepolymer containing epoxide groups and the polymer containing carboxylgroups can be modified by using silane-functional monomers, such as, forexample, γ-methacryloxypropyl-trimethoxysilane ormercaptopropyltrimethoxysilane. Alternatively, compounds containingsilane groups, such as, for example, methyltrimethoxysilane, can also beadded directly to the coatings. However, EP-A-212 457 contains no dataon suitable amounts of the silane components to be used. Furthermore,there is also no indication of the use of polysiloxane macromonomers.These coating agents known from EP-A-212 457 show only a smallimprovement in the surface properties of the resulting coatings, suchas, for example, water- and chemicals-repellency.

The present invention is thus based on the object of providing coatingagents which are based on acrylate copolymers containing carboxyl groupsand on epoxy resins and which lead to coatings which can be paintedover, have a good resistance to weathering, a good resistance tosolvents and chemicals, a good top coat appearance and adequate scratchresistance. For use in the field of automobile repair painting, thecoating agents furthermore should be hardenable at low temperatures andat the same time lead to surfaces which are dry to dust and tack-freeafter the shortest possible time. The coating agents furthermore shouldbe sandable, it should also be possible to paint over them withoutsanding the surface and they should have a good resistance to taping anduptake of spray mist.

This object is achieved, surprisingly, by a coating agent whichcomprises, as the binding agent, at least one polymer containingcarboxyl groups and, as the hardener, at least one epoxy resin having onaverage more than one epoxide group per molecule. The coating agent ischaracterized in that it comprises

at least one acrylate copolymer (A) which contains carboxyl groups andis obtainable by solution polymerization using less than 5% by weight,based on the total weight of the monomers employed for the preparationof copolymer (A), of one or more polysiloxane macromonomers al having anumber-average molecular weight of 1000 to 40,000 and on average 0.5 to2.5 ethylenically unsaturated double bonds per molecule, and/or

if appropriate one or more further epoxy resins.

The present invention furthermore relates to a process for thepreparation of coating agents according to one of claims 1 to 11, inwhich at least one polymer containing carboxyl groups, as the bindingagent, at least one epoxy resin, as the hardener, one or more organicsolvents, if appropriate pigments and/or fillers and if appropriatefurther auxiliaries and additives are mixed and if appropriatedispersed, characterized in that

A) at least one acrylate copolymer (A) which contains carboxyl groupsand is obtainable by solution polymerization using less than 5% byweight, based on the total weight of the monomers employed for thepreparation of copolymer (A), of one or more polysiloxane macromonomersal having a number-average molecular weight of 1000 to 40,000 and onaverage 0.5 to 2.5 ethylenically unsaturated double bonds per molecule,and/or

B) if appropriate one or more further epoxy resins are employed for thepreparation of the coating agents.

The present invention furthermore relates to processes for coatingsubstrates, in which these coating agents are applied, and to the use ofthese coating agents.

It is surprising and was not foreseeable that precisely the modificationaccording to the invention of coating agents based on binding agentscontaining carboxyl groups and on crosslinking agents containing epoxidegroups leads, by incorporation of polysiloxane macromonomers, to coatingagents which are distinguished by the resulting coatings having a goodcapacity for being painted over and a good resistance to weathering,chemicals and solvents. A significant improvement in the resistance totaping, the scratch resistance, the spray-ability and the top coatappearance (DOI) is furthermore advantageous.

It is essential to the invention that the coating agents comprise eitherat least one acrylate copolymer (A) which contains carboxyl groups andis modified by the polysiloxane macromonomers a₁, or at least oneacrylate copolymer (B) which contains epoxide groups and is modified bythe polysiloxane macromonomers a₁ or both at least one modified acrylatecopolymer (A) containing carboxyl groups and at least one modifiedacrylate copolymer (B) containing epoxide groups. Coating agents whichcomprise either only (A) or (B) as the modified component are preferred.Coating agents which comprise at least one modified acrylate copolymer(B) containing epoxide groups furthermore comprise, as the crosslinkingcomponent, at least one condensation and/or addition resin containingcarboxyl groups. Coating agents which comprise at least one modifiedacrylate copolymer (A) containing carboxyl groups accordingly alsocomprise, as the crosslinking component, at least one epoxy resin.Coating agents which comprise at least one acrylate copolymer (A) whichcontains carboxyl groups and is modified by the polysiloxanemacromonomers a₁, if appropriate further addition and/or condensationresins (C) containing carboxyl groups and, as the crosslinking agent,epoxy resins (component D) which are not modified by a₁ are particularlypreferred. Where possible, acrylate copolymers containing epoxide groupsare not used as the crosslinking agent, in particular because oftoxicological aspects.

Coating agents which comprise at least one acrylate copolymer (A) whichcontains carboxyl groups and is modified by the polysiloxanemacromonomers a₁, at least one polyester (C) containing carboxyl groupsand at least one epoxy resin (D) are especially preferred. Theindividual constituents of the coating agents according to the inventionwill now first be illustrated in more detail below.

It is essential to the invention that the coating agents contain atleast one acrylate copolymer which has been modified by incorporation ofone or more polysiloxane macromonomers a₁. Polysiloxane macromonomerswhich have a number-average molecular weight of 1000 to 40,000,preferably of 2000 to 10000, and on average 0.5 to 2.5, preferably 0.5to 1.5, ethylenically unsaturated double bonds per molecule are suitableboth for modification of acrylate copolymers (A) containing carboxylgroups and for modification of acrylate copolymers (B) containingepoxide groups.

Suitable components a₁ are, for example, the polysiloxane macromonomersdescribed in DE-OS 38 07 571 on pages 5 to 7, those described in DE-OS37 06 095 in columns 3 to 7, those described in EP-B 358 153 on pages 3to 6 and those described in U.S. Pat. No. 4,754,014 in columns 5 to 9.

Other acryloxysilane-containing vinyl monomers having the abovementionedmolecular weights and contents of ethylenically unsaturated double bondsfurthermore are also suitable, for example compounds which can beprepared by reaction of hydroxyl-functional silanes with epichlorohydrinand subsequent reaction of the reaction product with (meth)acrylic acidand/or hydroxyalkyl esters of (meth)acrylic acid.

Polysiloxane macromonomers of the following formula are preferablyemployed as component a₁ : ##STR1## where R₁ ═H or CH₃

R₂, R₃, R₄ and R₅ =identical or different aliphatic hydrocarbon radicalshaving 1 to 8 C atoms, in particular methyl, or the phenyl radical

n=2 to 5, preferably 3

m=8 to 30

The α,ω-acryloxyorganofunctional polydimethoxy-siloxane of the formula##STR2## with n≈9, an acryloxy equivalent of 550 g/equivalent, an OHnumber of 102 mg of KOH/g and a viscosity of 240 mPas (25° C.) isparticularly preferably employed.

Polysiloxane macromonomers which are preferably employed as component a₁are also those which have been prepared by reaction of 70 to 99,999 mol% of a compound (1) represented by the formula (1) ##STR3## in which R₁represents an aliphatic hydrocarbon group with to 8 C atoms or a phenylradical and R₂, R₃ and R₄ in each case represent a halogen radical or analkoxy radical having 1 to 4 C atoms or a hydroxyl group, with 30 to0,001 mol % of a compound (2), represented by the formula (II) ##STR4##in which R₅ represents a hydrogen atom or a methyl radical, R₆, R₇ andR₈ in each case represent halogen, OH or an alkoxy radical having 1 to 4C atoms or an aliphatic hydrocarbon group having 1 to 8 C atoms, atleast one of the radicals R₆, R₇ or R₈ being OH or an alkoxygroup, and nrepresents an integer from 1 to 6.

In the compound (1), examples of alkoxy groups having 1 to 4 C atoms arestraight-chain or branched groups, such as, for example, methoxy,ethoxy, propoxy, butoxy and the like. Examples of aliphatic hydrocarbongroups are straight-chain or branched aliphatic hydro-carbon groups,such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl andthe like. Methyl and phenyl are particularly preferred as R₁ in thecompound (1). Methoxy, ethoxy, propoxy, butoxy and hydroxyl arepreferred as R₂, R₃ and R₄. Examples of preferred compounds (1) aremethyltrimethoxysilane, phenyltrimethoxysilane, butyltrimethoxysilane,methyltriethoxysilane, methyltributoxysilane, phenyltrisilanol,methyltrisilanol and the like, of which methyltrimethoxysilane,phenyltrimethoxysilane and phenyltrisilanol are particularly preferred.These compounds can be used by themselves or in combination.

In the above compound (2), R₅ represents a hydrogen atom or a methylgroup and R₆, R₇ and R₈ in each case represent hydroxyl, alkoxy having 1to 4 carbon atoms or an aliphatic hydrocarbon group having 1 to 8 carbonatoms. n is an integer from 1 to 6. R₆, R₇ and R₈ can all be identicalor different or at least one of these groups can differ from the others.However, at least one of this group is hydroxyl or alkoxy.

In the compound (2), examples of aliphatic hydrocarbon groups having 1to 8 carbon atoms and alkoxy groups having 1 to 4 carbon atoms are thosewhich have been mentioned for compound (1). Methoxy, ethoxy and hydroxylgroups are particularly preferred as R₆, R₇ and R₈, and n is preferablyin the range from 2 to 4. Examples of preferred compounds (2) are

γ-acryloxyethyltriethoxysilane,

γ-methacryloxyethyltriethoxysilane,

γ-methacryloxypropyltrimethoxysilane,

γ-methacryloxypropyltriethoxysilane,

γ-acryloxypropyltrimethoxysilane,

γ-methacryloxybutyltriethoxysilane,

γ-acryloxypropyltrisilanol and the like.

Amongst these examples,

γ-acryloxyethyltriethoxysilane,

γ-methacryloxyethyltriethoxysilane,

γ-methacryloxypropyltrimethoxysilane,

γ-methacryloxypropyltriethoxysilane and

γ-acryloxypropyltrisilanol

are particularly preferred.

These compounds can be employed individually or in combination.

The reaction between compounds (1) and (2) is effected by dehydratingcondensation of the hydroxyl groups contained in these compounds and/orof the hydroxyl groups which are due to hydrolysis of the alkoxy groupsof these compounds. Depending on the reaction conditions, the reactioncomprises, in addition to the dehydrating reaction, a dealcoholizingcondensation. If the compounds (1) or (2) contain halogen radicals, thereaction between (1) and (2) is effected by dehydrohalogenation.

Although the reaction can be carried out in the absence of solvents, itis desirable to carry out the reaction in water and/or an organicsolvent in which the two compounds (1) and (2) are soluble. Examples ofsuitable organic solvents are hydrocarbon solvents, such as, forexample, heptane, toluene, xylene, octane and white spirit, estersolvents, such as, for example, ethyl acetate, n-butyl acetate, isobutylacetate, methylcellusolve acetate and butylcarbitol acetate, ketonesolvents, such as, for example, methyl ethyl ketone, methyl isobutylketone and diisobutyl ketone, alcoholic solvents, such as, for example,ethanol, isopropanol, n-butanol, sec-butanol and isobutanol, ethersolvents, such as, for example, n-butyl ether, dioxane, ethylene glycolmonomethyl ether and ethylene glycol monoethyl ether, and the like.These solvents can be used individually or in combination.

If the compounds (1) and (2) are used in the form of a solution, thetotal concentration of these compounds in the solution is suitably atleast 5% by weight. The compounds (1) and (2) are reacted in a suitablemanner at temperatures from approximately 20° to approximately 180° C.,preferably approximately 50° to approximately 120° C. The reaction timeis suitably usually approximately 1 to approximately 40 hours.

If appropriate, the reaction can be carried out in the presence of apolymerization inhibitor which effectively prevents the polymerizationreaction on the basis of unsaturated bonds in the compound (2). Examplesof suitable inhibitors are hydroquinone, hydroquinone monomethyl etherand similar quinone compounds. The reaction system of the compounds (1)and (2) for the preparation of the polysiloxane macromonomers cancomprise tetraalkoxysilane, dialkyldialkoxysilane or the like, which areemployed in an amount of up to approximately 20 mol %, based on thetotal weight of compounds (1) and (2). If R₂, R₃, R₄, R₆, R₇ and R₈ inthe compounds (1) and (2) all represent hydroxyl, it is desirable tocarry out the reaction in an organic solvent, while heating andstirring, for the purpose of dehydrating condensation. If furthermore atleast one of the compounds (1) and (2) contains Si-bonded alkoxy groups,it is preferable to carry out a hydrolysis before the condensation. Itbecomes necessary to carry out the hydrolysis if all the groups R₂, R₃,R₄, R₆, R₇ and R₈ are alkoxy groups. The hydrolysis reaction and thecondensation reaction can be carried out continuously in the presence ofwater and a catalyst, while heating and stirring. The amount of waterused for this reaction is preferably at least approximately 0.1 mol permol of alkoxy, although it is not limited in particular. If less than0.1 mol of water is present, the two compounds tend to become lessreactive. The use of a large excess of water is particularly preferred.In the case where the condensation reaction produces an alcohol which issparingly soluble in water, the use of a combination of water and awater-soluble organic solvent serves to render the reaction systemhomogeneous. The above-mentioned alcoholic ester, ether and ketonesolvents are preferably used as the water-soluble organic solvent. Acidor alkaline catalysts can be employed as catalysts for the hydrolysisreaction. Examples of suitable acid catalysts are hydrochloric acid,sulfuric acid, phosphoric acid, formic acid, acetic acid, propionicacid, acrylic acid, methacrylic acid and the like.

Examples of suitable alkaline catalysts are sodium hydroxide,triethylamine, ammonia and the like. It is advantageous to employ thecatalyst in an amount of approximately 0.0001 to approximately 5% byweight, preferably approximately 0.01 to approximately 0.2% by weight,based on the total amount of the compounds (1) and (2).

The amount of polysiloxane macromonomer or macromonomers a₁ employed formodification of the acrylate copolymer (A) containing carboxyl groups isless than 5% by weight, preferably 0.05 to 2.5% by weight, particularlypreferably less than 1% by weight and especially preferably 0.05 to 0.5%by weight, in each case based on the total weight of the total monomers(including al) employed for the preparation of copolymer (A).

The amount of polysiloxane macromonomer or macromonomers a₁ employed formodification of the acrylate copolymer (B) containing epoxide groups isless than 5% by weight, preferably 0.05 to 2.5% by weight, particularlypreferably less than 1% by weight and especially preferably 0.05 to lessthan 0.5% by weight, in each case based on the total weight of the totalmonomers (including a₁) employed for the preparation of copolymer (B).

An increase in content of polysiloxane macromonomer or macromonomers a₁here leads to a decrease in the capacity of the resulting coatings forbeing painted over, the occurrence of flow disturbances and clouding ofthe acrylate copolymer solution and the coating agents preparedtherefrom, and to siliconization of the spray plant and thereforeproblems in changing the paint.

The most favorable content of polysiloxane macromonomer(s) in each casetherefore depends on the desired properties of the coatings and hence onthe intended use. However, the most favorable amount to be employed forthe particular intended use can be determined easily with the aid of afew experiments.

To prepare the acrylate copolymers (A) containing carboxyl groups, allthe monomers usually employed can be used together with the polysiloxanemacromonomers. Acrylate copolymers (A) which are preferably employed areobtainable by copolymerization of

a₁) 0.05 to 2.5% by weight, preferably 0.05 to 0.5% by weight, of one ormore polysiloxane macromonomers a₁,

a₂) 0 to 40% by weight, preferably 0 to 30% by weight, of one or moreethylenically unsaturated monomers containing carboxyl groups,

a₃) 0 to 40% by weight, preferably 0 to 30% by weight, of one or morevinylaromatic hydrocarbons,

a₄) 0 to 99.95% by weight, preferably 20 to 60% by weight, of one ormore ethylenically unsaturated monomers containing hydroxyl groups,

a₅) 0 to 30% by weight, preferably 0 to 20% by weight, of one or moremonomers having at least two polymerizable, ethylenically unsaturateddouble bonds and

a₆) 0 to 80% by weight of one or more other ethylenically unsaturatedcopolymerizable monomers,

wherein the sum of the parts by weight of components a₁ to a₆ is in eachcase 100% by weight and wherein the amounts of components a₂ and a₄employed should not both simultaneously be zero.

If this copolymer prepared in this way contains hydroxyl groups, it canbe reacted, if appropriate, with carboxylic acid anhydrides in a furtherstage, the amount of carboxylic acid anhydrides employed being chosen sothat the copolymer (A) formed has the desired acid number.

The compounds suitable as component a₁ are the polysiloxanemacromonomers already described above.

Examples of suitable monomers a₂ containing carboxyl groups areunsaturated carboxylic acids, such as, for example, acrylic,methacrylic, itaconic, crotonic, isocrotonic, aconitic, maleic andfumaric acid, half-esters of maleic and fumaric acid, as well asβ-carboxyethyl acrylate and adducts of hydroxyalkyl esters of acrylicacid and/or methacrylic acid with carboxylic acid anhydrides, such as,for example, mono-2-methacryloyloxyethyl phthalate. The amounts ofcomponent a₂ is sic! 0 to 40% by weight, preferably 0 to 30% by weight.

Component a₃ is a monovinylaromatic compound. It preferably contains 8to 9 carbon atoms per molecule. Examples of suitable compounds arestyrene, vinyltoluenes, α-methylstyrene, chlorostyrenes, o-, m- orp-methylstyrene, 2,5-dimethylstyrene, p-methoxystyrene,p-tert-butylstyrene, p-dimethylaminostyrene, p-acetamidostyrene andm-vinylphenol. Vinyltoluenes and, in particular, styrene are preferablyemployed. The amount of component a₃ is 0 to 40% by weight, preferably 0to 30% by weight.

Possible components a₄ are hydroxyalkyl esters of α,β-unsaturatedcarboxylic acids with primary or secondary hydroxyl groups. Hydroxyalkylesters with primary hydroxyl groups are predominantly employed, sincethey have a higher reactivity in the polymer-analogous reaction with thecarboxylic acid anhydride. Mixtures of hydroxyalkyl esters havingprimary hydroxyl groups and hydroxyalkyl esters having secondaryhydroxyl groups can of course also be used, for example if hydroxylgroups are required in the copolymer containing carboxyl groups, forexample for establishing compatibility of the copolymer containingcarboxyl groups.

Examples of suitable hydroxyalkyl esters of α,β-unsaturated carboxylicacids having primary hydroxyl groups are hydroxyethyl acrylate,hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyamyl acrylate,hydroxyhexyl acrylate, hydroxyoctyl acrylate and the correspondingmethacrylates. Examples which may be mentioned of hydroxyalkyl esterswhich have a secondary hydroxyl group and can be used are2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutylacrylate and the corresponding methacrylates.

The corresponding esters of other α,β-unsaturated carboxylic acids, suchas, for example, of crotonic acid and of isocrotonic acid, can in eachcase of course also be used.

Component a₄ advantageously can be at least in part a reaction productof one mol of hydroxyethyl acrylate and/or hydroxyethyl methacrylate andon average two mols of ε-caprolactone.

Compounds which advantageously can be used as component a₅ are those ofthe general formula ##STR5## in which: X=O, NR' or S, where R═H, alkylor aryl, and

n=2 to 8.

Component a₅ can be a reaction product with a polymerizable,olefinically unsaturated double bond, acrylic acid being excluded, andglycidyl methacrylate. Saturated and/or unsaturated polycarboxylic acidsesterified with an unsaturated alcohol containing a polymerizable doublebond, or unsaturated monocarboxylic acids esterified with an unsaturatedalcohol containing a polymerizable double bond, with the exception ofderivatives of acrylic acid, furthermore are suitable. Components a₅advantageously are chosen from products which are prepared frompolyisocyanates with unsaturated alcohols or a mines containingpolymerizable double bonds, such as, for example, the reaction productof 1 mol of hexamethylene diisocyanate with 2 mol of allyl alcohol.Esters of polyethylene glycol and/or polypropylene glycol having anaverage molecular weight of less than 1500, preferably less than 1000,and (meth)acrylic acid furthermore are furthermore possible.

Examples of polyethylenically unsaturated compounds are hexanedioldimethacrylate, glycol dimethacrylate, butanediol dimethacrylate,trimethylolpropane trimethacrylate, divinylbenzene and similarcompounds.

If appropriate, other ethylenically unsaturated copolymerizable monomersa₆ can also be employed for building up the copolymer (A) containingcarboxyl groups. When choosing these monomers, it should be ensured thatthe incorporation of these monomers a₆ does not lead to undesirableproperties of the copolymer. The choice of component a₆ thus largelydepends on the desired properties of the hardenable composition withrespect to elasticity, hardness, compatibility and polarity. The contentof monomers containing epoxide groups is preferably less than 2% byweight, based on the weight of the monomer mixture. Copolymer (A) isparticularly preferably largely free from epoxide groups (<0.1% byweight).

Alkyl esters of olefinically unsaturated carboxylic acids are preferablyemployed as component a₆. Examples of these are methyl (meth)acrylate,ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate,isopropyl (meth)acrylate, isobutyl (meth)acrylate, pentyl(meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate,cyclohex-yl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl(meth)acrylate, 3,5,5-trimethylhexyl (meth)acrylate, decyl(meth)acrylate, dodecyl (meth)acrylate, hexadecyl (meth)acrylate,octadecyl (meth)acrylate, octadecenyl (meth)acrylate and thecorresponding esters of maleic, fumaric, tetrahydrophthalic, crotonic,isocrotonic, vinylacetic and itaconic acid.

Compounds which are furthermore suitable as component a₆ are otherethylenically unsaturated compounds, such as, for example, alkoxyethylacrylates, aryloxyethyl acrylates and the corresponding methacrylates,such as, for example, butoxyethyl (meth)acrylate and phenoxyethyl(meth)acrylate; unsaturated compounds having tertiary amino groups, suchas, for example, N,N'-diethylaminoethyl methacrylate, 2-vinylpyridine,4-vinylpyridine, vinylpyrroline, vinylquinoline, vinylisoquinoline,N,N'-dimethylaminoethyl vinyl ether and 2-methyl-5-vinylpyridine; andcompounds such as, for example, acrylonitrile, methacrylonitrile,acrolein and methacrolein.

Vinyl esters of monocarboxylic acids, preferably vinyl esters ofmonocarboxylic acids which are branched in the α-position and have 5 to15 C atoms per molecule, are also suitable as component as. The branchedmonocarboxylic acids can be obtained by reaction of formic acid orcarbon monoxide and water with olefins in the presence of a liquid,strongly acid catalyst; the olefins can be cracking products ofparaffinic hydrocarbons, such as petroleum fractions, and can compriseboth branched and straight-chain acyclic and/or cycloaliphatic olefins.In the reaction of such olefins with formic acid or with carbon monoxideand water, a mixture of carboxylic acids in which the carboxyl group ispredominantly on a quaternarycarbon atom is formed. Other olefinicstarting substances are, for example, propylene trimer, propylenetetramer and diisobutylene. The vinyl esters can also be prepared fromthe acids in a manner which is known per se, for example by allowing theacids to react with acetylene.

Vinyl esters of saturated aliphatic monocarboxylic acids which have 9-11C atoms and are branched on the α-C atom are particularlypreferred--because of their good availability. The vinyl ester ofp-tert-butylbenzoic acid is moreover particularly preferred. Examples offurther suitable vinyl esters are vinyl acetate and vinyl propionate.

To prepare the acrylate copolymers (B) containing epoxide groups, allthe monomers usually employed can likewise be employed together with thepolysiloxane macromonomers. The epoxide groups can be introduced intocopolymer (B) here by using monomers containing epoxide groups.Copolymers (B) which are preferably employed are obtainable bycopolymerization of

e₁) 0.05 to 2.5% by weight, preferably 0.05 to less than 0.5% by weight,of one or more polysiloxane macromonomers a₁,

e₂) 10 to 50% by weight, preferably 15 to 35% by weight, of one or moreethylenically unsaturated monomers containing epoxide groups,

e₃) 0 to 40% by weight, preferably 0 to 30% by weight, of one or morevinylaromatic hydrocarbons,

e₄) 0 to 30% by weight, preferably 0 to 20% by weight, of one or moremonomers having at least two polymerizable, ethylenically unsaturateddouble bonds and

e₅) 0 to 89.95% by weight of one or more ethylenically unsaturatedcopolymerizable monomers,

the sum of the parts by weight of components e₁ to e₃ being in each case100% by weight.

Examples of suitable monomers are the compounds already mentioned in thedescription of copolymer (A). Copolymers (A) and (B) are obtainable bysolution polymerization of the monomers. The polymerization ispreferably carried out with exclusion of oxygen, for example by workingin a nitrogen atmosphere. The reactor is equipped with correspondingstirring, heating and cooling devices and with a reflux condenser, inwhich volatile constituents, such as, for example, styrene, areretained. The polymerization reaction is preferably carried out attemperatures of 90° to 160° C., particularly preferably 110° to 140° C.,using polymerization initiators and if appropriate polymerizationregulators.

Suitable free radical initiators are organic peroxides, such as, forexample, dibenzoyl peroxide, dicumyl peroxide, cumene hydroperoxide,di-tert-butyl peroxide, tert-butylamide peroxide, tert-butylhydroperoxide, 2,2-di-tert-butyl peroxybutane, tert-amyl perbenzoate,1,3-bis(tert-butyl peroxyisopropyl)-benzene, diisopropylbenzenemonohydroperoxide and diacyl peroxides, such as, for example, diacetylperoxide, peroxyketals, such as, for example,2,2-di-(tert-amylperoxy)-propane and ethyl3,3-di-(tert-amylperoxy)-butyrate, and heat-labile highly substitutedethane derivatives, for example those based on silyl-substituted ethanederivatives and based on benzopinacol. Aliphatic azo compounds, such as,for example, azobiscyclohexanenitrile, furthermore can also be employed.

The amount of initiator in most cases is 0.1 to 5% by weight, based onthe amount of monomer to be processed, but it can also be higher, ifappropriate. Usually, the initiator, dissolved in some of the solventemployed for the polymerization, is metered in gradually during thepolymerization reaction. The initiator addition preferably takes about 1to 2 hours longer than the monomer addition, so that a good action isthus also achieved during the after-polymerization phase. If initiatorswith only a slow rate of dissociation, that is to say a long half-life,under the reaction conditions which exist are employed, it is alsopossible for the initiator to be initially introduced.

The reaction is preferably carried out in the presence of polymerizationregulators, since clouding of the polymer solutions can be avoidedbetter in this way. Suitable regulators are, preferably, mercaptocompounds, mercaptoethanol particularly preferably being employed. Otherpossible regulators are, for example, alkylmercaptans, such as, forexample, t-dodecylmercaptan, octylmercaptan, phenylmercaptan,octyldecylmercaptan and butylmercaptan, and thiocarboxylic acids, suchas, for example, thioacetic acid or thiolactic acid.

These regulators are employed in an amount of up to 2% by weight, basedon the amount of monomer to be processed. They are preferably dissolvedin one of the monomer additions and added with the monomers. The amountof regulator added is preferably constant with respect to time.

The polymerization is carried out in an organic solvent which is inerttoward the monomer employed and if appropriate toward carboxylic acidanhydrides. The polymerization solids content is preferably at least 50%by weight, particularly preferably between 60 and 75% by weight, basedon the total weight of the reaction mixture. Examples of suitablesolvents are commercially available alkylated aromatic hydrocarbons ormixtures having a boiling range of 150° to 220° C., xylene and otheraromatic hydrocarbons, esters, such as, for example, butyl acetate,butylglycol acetate, ethyl ethoxypropionate and the like, and aliphatichydrocarbons and the like.

The copolymerization of the monomer components is preferably carried outas follows:

At least 10% by weight, preferably 100% by weight, of the total amountof component a₁ to be employed is initially introduced into the reactortogether with some of the total amount of solvent to be employed, andthe mixture is heated up to the particular reaction temperature. Theremaining amount of solvent is preferably added--as alreadydescribed--gradually together with the catalyst. Any remaining amount ofcomponent a₁ which still exists and the other monomers (components a₂ toa₆) are metered in.

If vinyl ester monomers are employed for the preparation of the acrylatecopolymer (A) or (B), preferably at least 60% by weight, particularlypreferably 100% by weight, of the total amount of the vinyl ester isalso added in the initial mixture.

This specific polymerization process promotes, as is assumed,copolymerization and reduces homopolymerization of the individualcomponents. In addition, copolymers which have a very low residualmonomer content and give clear solutions having a high solids contentare obtained.

The copolymers (A) employed according to the invention preferably have anumber-average molecular weight of 5000 to 25000.

The acrylate copolymer (A) containing carboxyl groups usually has anacid number of 40 to 150 mg of KOH/g, preferably of 60 to 120 mg ofKOH/g. Copolymer (A) furthermore can also contain carboxyl groups and/ortertiary amino groups. Preferred acrylate copolymers (A) have an aminenumber of 0 to 100 mg of KOH/g, preferably of 10 to 70 mg of KOH/g, andan OH number of 0 to 110 mg of KOH/g, preferably of 20 to 90 mg ofKOH/g.

The carboxyl groups required for hardening the coating agents can beintroduced at least in part using monomers containing carboxyl groupswhen building up the acrylate copolymers (A). However, it is alsopossible for at least some of the carboxyl groups of the copolymer to beintroduced by addition of carboxylic acid anhydrides onto copolymerscontaining hydroxyl groups.

The copolymers employed for the reaction with the carboxylic acidanhydrides here usually have an OH number of 40 to 250 mg of KOH/g,preferably of 80 to 140 mg of KOH/g.

Carboxylic acid anhydrides which are suitable for addition onto thecopolymers containing hydroxyl groups are the anhydrides of aliphatic,cycloaliphatic and aromatic saturated and/or unsaturated di- andpolycarboxylic acids, such as, for example, the anhydrides of phthalicacid, tetrahydrophthalic acid, hexahydrophthalic acid, succinic acid,maleic acid, itaconic acid, glutaric acid, trimellitic acid andpyromellitic acid, and halogenated or alkylated derivatives thereof.

Anhydrides of phthalic acid and tetrahydro- and hexahydrophthalic acidand 5-methylhexahydrophthalic anhydride are preferably employed.

The reaction of the copolymers containing hydroxyl groups with thecarboxylic acid anhydrides is carried out at temperatures of 100° to140° C. in the presence of a catalyst, such as, for example, tertiaryamines.

On the other hand, if the copolymers containing hydroxyl groups containtertiary amino groups - for example by using monomers having tertiaryamino groups or by prior reaction of the copolymers containing hydroxylgroups with compounds V, which contain on average 0.8 to 1.5, preferably1, free isocyanate groups and at least one tertiary amino group permolecule--a catalyst can be dispensed with and the reaction can becarried out at low temperatures of 50° to 130° C.

It is particularly advantageous if tertiary amino groups areincorporated into the copolymer containing carboxyl groups, since theycatalyze subsequent crosslinking of the copolymers containing carboxylgroups with epoxide groups and the baking temperatures of coating agentsbased on these polymers are thus reduced.

If the copolymer contains tertiary amino groups, it must be ensured inthe case of addition of unsaturated carboxylic acid anhydrides, such as,for example, in the case of addition of maleic anhydride, that nosolvents which react with the unsaturated carboxylic acid anhydrideunder catalysis by the tertiary nitrogen groups are employed. Thus, forexample, acetone, methyl ethyl ketone, butyl acetate and otheracetylating solvents cannot be used. Hydrocarbons and polar solvents,such as dimethylformamide, dimethylacetamide, n-methylpyrrolidone sic!and the like can be used.

The tertiary amino groups are preferably introduced by reacting thepolymer containing hydroxyl and carboxyl groups with compounds V whichcontain on average 0.8 to 1.5, preferably 1, free isocyanate groups andat least one tertiary amino group per molecule. However, it is alsopossible for the copolymer containing hydroxyl groups first to bereacted with the compounds V and only then for the carboxyl groups to beintroduced into the copolymer by reaction with a carboxylic acidanhydride. In this case--as already mentioned--the reaction with theanhydride can be carried out at low temperatures.

The amount of compound V is chosen here so that the resin formed has anamine number of up to 100 mg of KOH/g. If the copolymers are to beemployed in coating agents which are hardened at room temperature, ahigher amine number of 10 to 70 mg of KOH/g is established.

The compounds V used to introduce the tertiary amino groups are preparedby reacting diisocyanates or polyisocyanates with a stoichiometricdeficit of a tertiary amine. Tertiary amines which are suitable for thisreaction are those of the general formula NR₁ R₂ R₃, wherein R₁preferably denotes an alkanol radical or another radical containinghydroxyl groups and R₂ and R₃ can be alkyl or cycloalkyl radicals.Dialkylalkanolamines, such as, for example, dimethylethanolamine,diethylethanolamine and higher homologues or isomers thereof, arepreferred.

Examples of suitable di- or polyisocyanates are: Aromatic isocyanates,such as, for example, toluylene 2,4- and 2,6-diisocyanate and mixturesthereof, diphenylmethane 4,4'-diisocyanate, m-phenylene diisocyanate,p-phenylene diisocyanate, diphenylene 4,4'-diisocyanate, naphthalene1,5-diisocyanate, naphthalene 1,4-diisocyanate, toluidine4,4'-diisocyanate, xylylene diisocyanate and substituted aromaticsystems, such as, for example, dianisidine diisocyanates, diphenyl ether4,4'-diisocyanates and chlorodiphenylene diisocyanates, and aromaticisocyanates of higher functionality, such as, for example,1,3,5-triisocyanatobenzene, 4,4',4"-triisocyanato-triphenylmethane sic!,2,4,6-triisocyanatotoluene and 4,4'-diphenyldimethane2,2',5,5'-tetraisocyanate; cycloaliphatic isocyanates, such as, forexample, cyclopentane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate,cyclohexane 1,2-diisocyanate and isophorone diisocyanate; and aliphaticisocyanates, such as, for example, trimethylene, tetramethylene,pentamethylene, hexamethylene and trimethylhexamethylene1,6-diisocyanate and trishexamethylene triisocyanate.

Diisocyanates having isocyanate groups of different reactivity, such as,for example, isophorone diisocyanate, are preferably employed.

The reaction between the amine and the isocyanate is carried out attemperatures from 0° to 80° C., preferably from 20° to 50° C. Theproportions of the reaction partners are chosen so that the compound Vformed contains 0.8 to 1.5, preferably 1, free isocyanate groups.

In addition to or instead of the acrylate copolymers (A) containingcarboxyl groups, the coating agents according to the invention can alsocomprise, if appropriate, further addition and/or condensation resinscontaining carboxyl groups. All the resins usually employed in coatingagents are suitable for this purpose. The choice of these resins dependslargely on the desired properties of the coating agents in respect ofelasticity, hardness, compatibility, polarity and the like. Resinshaving an acid number of 10 to 160 mg of KOH/g, particularly preferably20 to 120 mg of KOH/g, are preferably employed as component C. Ifappropriate, the resins C additionally can also contain tertiary aminogroups and/or hydroxyl groups. The resins C preferably have aminenumbers of 0 to 90 mg of KOH/g and/or OH numbers of 0 to 250 mg ofKOH/g.

A mixture of 10 to 95% by weight, preferably 40 to 90% by weight, ofcomponent (A) and 90 to 5% by weight, preferably 10 to 60% by weight, ofat least one polyester (component C) which contains carboxyl and aminogroups and has an acid number of 10 to 160, preferably 20 to 120 mg ofKOH/g, and an amine number of 0 to 90, preferably 10 to 60 mg of KOH/g,is particularly preferably employed as the binding agent in the coatingagents according to the invention. The sum of the amounts by weight ofcomponents (A) plus (C) here is in each case 100% by weight. For lowcontents of component (A), copolymers having a relatively high contentof a₁ are employed as component (A).

The polyester is obtainable by reaction of

P1) polycarboxylic acids or anhydrides thereof, if appropriate togetherwith monocarboxylic acids,

P2) polyols, if appropriate together with monools, and if appropriate

P3) further modifying components, and if appropriate

P4) a component which can react with the reaction product of P1, P2 andif appropriate P3,

with the proviso that the end product contains tertiary amino groupswhich originate from component P1 and/or P2 and/or P4.

Suitable polycarboxylic acids (component P1) for the preparation of thepolyesters are, for example, phthalic acid, isophthalic acid,terephthalic acid, halogenophthalic acids, such as tetrachloro- andtetrabromophthalic acid, hexahydrophthalic acid, adipic acid, sebacicacid, fumaric acid, maleic acid, endomethylene-tetrahydrophthalic acid,1,1,3-trimethyl-3-phenylindane-4,5-dicarboxylic acid, trimellitic acidand anhydrides of the acids mentioned, where these exist.

To prepare polyesters having the lowest possible color number, the useof aliphatic and cycloaliphatic polycarboxylic acids or of anhydridesthereof which are not prepared by the Oxo process is preferred. The useof cyclohexanedicarboxylic acid is particularly preferred, since itleads to colorless polymers which furthermore at the same time lead to agood drying and development of hardness in the paint film. Ifappropriate, monocarboxylic acids, such as, for example, benzoic acid,tertbutylbenzoic acid, lauric acid, isononanoic acid and fatty acids ofnaturally occurring oils, can also be employed together with thepolycarboxylic acids.

In a preferred embodiment, aminocarboxylic acids having at least onetertiary amino group can be used, inter alia or exclusively, ascomponent P1 (carboxylic acid component). Examples of these are:pyridine-2-carboxylic acid, pyridine-3-carboxylic acid,pyridine-4-carboxylic acid and pyridine-2,6-dicarboxylic acid. Nicotinicacid, that is to say pyridine-3-carboxylic acid, is preferably used herebecause it is a very reactive aminocarboxylic acid in respect ofcatalyzing the acid/epoxide reaction.

The reaction product of anaminoalcohol having at least one tertiaryamino group and a polycarboxylic acid anhydride can also be usedadvantageously as component P1. The reaction product of2-hydroxyethyl-piperidine with phthalic anhydride may be mentioned as anexample here.

The reaction product of a polyamine having at least one tertiary and atleast one primary or secondary, preferably secondary, amino group and apolycarboxylic acid anhydride furthermore can be used as component P1.

Suitable alcohol components P2 for the preparation of the polyester arepolyhydric alcohols, such as ethylene sic! glycol, propanediols,butanediols, pentanediols, hexanediols, neopentylglycol, diethyleneglycol, cyclohexanedimethanol, trimethylpentanediol,ditrimethylolpropane sic!, trimethylolethane, trimethylolpropane,glycerol, pentaerythritol, dipentaerythritol, trishydroxyethylisocyanurate, polyethylene glycol and polypropylene glycol, ifappropriate together with monohydric alcohols, such as, for example,butanol, octanol, lauryl alcohol and ethoxylated or propoxylatedphenols.

Aminoalcohols having at least one tertiary amino group preferably can beused, inter alia or exclusively, as the alcohol component P2. Examplesof these which may be mentioned are 2-hydroxyethylpyridine,dimethylaminopropanol, methyldiethanolamine, methyldipropanolamine anddihydroxyethylaniline. Reaction products of epoxy resins with carboxylicacids and/or amines likewise are preferably employed as the alcoholcomponent P2.

The reaction product of low molecular weight epoxy resins withpolycarboxylic acids and/or polycarboxylic acid anhydrides andaminocarboxylic acids having at least one tertiary amino group and/orpolyamines having at least one tertiary and at least one primary orsecondary amino group, the product subsequently also being esterified,if appropriate, with the acid and the alcohol component and beingmodified, if appropriate, with polyisocyanates, can thus be used as thealcohol component P2. Low molecular weight epoxy resins are to beunderstood as epoxy resins having a molecular weight of less than about2000.

If epoxy resins are used, low-chlorine types should be employed, sinceotherwise severe discoloration of the products may occur.

Polyisocyanates and/or diepoxide compounds, and if appropriate alsomonoisocyanates and/or monoepoxide compounds, are preferably used as themodified sic! component P3. Suitable polyisocyanates are, for example,the toluylene diisocyanates, hexamethylene diisocyanate and isophoronediisocyanate. Diepoxide compounds are to be understood as epoxy resinshaving on average about two epoxide groups per molecule. Suitablemonoepoxide compounds are, for example, olefin oxides, such as octyleneoxide, butyl glycidyl ether, allyl glycidyl ether, phenyl glycidylether, p-butylphenol glycidyl ether, cresyl glycidyl ether, styryloxide, glycidyl methacrylate, cyclohexenevinyl monoxide, dipentenemonoxide, α-pinene oxide and glycidyl esters of tertiary carboxylicacids.

Monoisocyanates having at least one tertiary amino group are preferablyused as components P4 which can react with the reaction product of P1,P2 and if appropriate P3. These monoisocyanates can be prepared, forexample, by reaction of suitable diisocyanates, such as isophoronediisocyanate, with aminoalcohols having a tertiary amino group, such as,for example, hydroryethylpyridine or dimethylaminoethanol, or withpolyamines having at least one tertiary and at least one secondary orprimary amino group. The monoisocyanates are bonded to the binding agentsystem by reaction with free hydroxyl groups of the polycondensationand/or addition product to form a urethane bond.

Polyamines having at least one tertiary and at least one primary orsecondary amino group can also be used as component P4. An example whichmay be mentioned here is dimethylaminopropylmethylamine.

The ring-opening product of epoxy resins with compounds having an activehydrogen can also be used as the alcohol component. Thus, for example,first diepoxides, such as the known Epikote types, can be reacted firstin stages with dicarboxylic acids, such as, for example,pyridine-2,6-dicarboxylic acid, to give a precursor, which is thenfurther employed as the alcohol component.

Further components P1 to P2 sic! which are suitable for building up thepolyester resin can be found in German Patent Application 36 29 470.

It is important in all cases that the resulting end product has an acidnumber in the range from 10 to 160, preferably from 20 to 120, and anamine number in the range from 0 to 90, preferably 10 to 60. Too severea discoloration of the products during the condensation is avoided byaddition of antioxidants or reducing agents, such as, for example,hypophosphorous acid.

The polyesters and acrylates containing carboxyl and tertiary aminogroups are prepared from the compounds mentioned in the customarymanner.

For all two-stage variants in which a cyclic acid anhydride is addedonto a polymer containing hydroxyl groups, it is preferable for theinitial dissolving of the resin after the addition to be carried out notwith primary but with secondary or tertiary alcohols, in order thus tosuppress the alcoholysis of the half-ester bond which proceeds as a sidereaction.

The coating agent according to the invention comprises at least oneepoxy resin having on average more than one epoxide group per moleculeas the crosslinking agent for the reaction with the carboxyl groups ofcopolymer (A) and/or of resin (C). The amounts of binding agent andhardener employed are usually chosen so that the ratio of acid groups ofthe binding agent (component (A) and/or component (C)) to the epoxidegroups of the hardener (component (B) and/or (D)) is in the range from0.3:1 to 3:1.

The total amount of binding agent plus hardener employed (without thesolvent content) is usually between 30 and 70% by weight, based on thetotal weight of the coating agent.

Component (B) and/or (D) are employed as the crosslinking agentcomponent. Particularly preferred coating agents comprise, in additionto the acrylate copolymers (A) containing carboxyl groups and ifappropriate further resins (C) containing carboxyl groups, the epoxyresins (D) as the crosslinking agent.

The acrylate copolymers (B) which contain epoxide groups and aresuitable as the crosslinking agent have already been described in pages26 to 27 of the present description.

The copolymers (B) employed according to the invention preferably have anumber-average molecular weight of 800 to 2200. The epoxide equivalentweight of the copolymers (B) is preferably between 250 and 550.

Examples of the epoxy resins employed as component (D) are compoundshaving at least two epoxide groups per molecule, for examplecondensation products of epichlorohydrin and bisphenol A, and thecycloaliphatic bisepoxides which correspond to the formulae (I) and(II): ##STR6##

Substances which furthermore are suitable as component (D) are, forexample, epoxidation products of naturally occurring fats, oils, fattyacid derivatives, modified oils and epoxidized polybutadienes, which areformed by reaction of commercially available polybutadiene oils withperacids or organic acid/H₂ O₂ mixtures, novolaks containing epoxidegroups, glycidyl ethers of a polyhydric alcohol, for example ethyleneglycol diglycidyl ether, glycerol polyglycidyl ether, sorbitolpolyglycidyl ether, trimethylolpropane polyglycidyl ether andpentaerythritol polyglycidyl ether, and low molecular weight acrylateresins having oxirane groups in side chains.

Substances which furthermore can also advantageously be employed as thecrosslinking agent (D) are reaction products of polyepoxides containinghydroxyl groups with di- or polyisocyanates, such as are formed, forexample, by reaction of OH-functional epoxides, such as, for example,before sic! sorbitol polyglycidyl ethers, with isophorone diisocyanate.

Polar epoxides, for example based on a reaction product of melamineresins with acrylamide, the acrylic double bond subsequently beingepoxidized, are also employed as preferred crosslinking agents (D). Anexample of this substance class which may be mentioned is the commercialproduct Santolink LSE 4103 from Monsanto, in which the epoxy resin basestructure is a dinuclear melamine, the molecular weight is about 1200and the epoxide equivalent weight is about 300.

If appropriate, a crosslinking catalyst can be used to catalyze thecarboxy/epoxy reaction. Catalysts which are particularly suitable hereare tertiary amines, quaternary ammonium compounds, such as, forexample, benzyltrimethylammonium chloride, specific chromium compoundsand tin compounds. The use of a crosslinking catalyst is of courseunnecessary in most cases where tertiary amino groups are alreadyincorporated into the acrylate copolymer. Lower baking temperatures andshorter baking times are achieved by using an internal or externalcrosslinking catalyst. The crosslinking catalyst is preferably used inan amount of 0.5 to 10% by weight, based on the weight of the epoxidecomponent.

Solvents which are suitable for the coating agents according to theinvention are, for example, toluene, xylene, butanol, ethyl acetate,butyl acetate, pentyl acetate, dimethyl glutarate, dimethyl succinate,1-methoxyprop-2-yl acetate, 2-ethylhexanol, ethylene glycol diacetate,ethylene glycol monoethyl and -butyl ether or acetates thereof, ethyleneglycol dimethyl ether, diethylene glycol dimethyl ether, gasolinescontaining aromatics, cyclohexanone, methyl ethyl ketone, acetone, butylacetoxyglycolate and ethyl acetoxyglycolate.

These solvents can be employed individually or as a mixture of varioussolvents.

The coating agents according to the invention moreover can contain, ifappropriate, pigments as well as auxiliaries and additives. Suitableadditives and auxiliaries are, for example, fillers, such as, forexample, talc, mica, kaolin, chalk, quartz flour, asbestos flour, bariumsulfate, silicates and glass fibers, and antisettling agents, such as,for example, finely divided silicic acid, bentonite, colloidal silicatesand the like; flow agents, silicone oils, plasticizers, such asphosphoric acid esters and phthalic acid esters, viscosity-controllingadditives, matting agents, UV absorbers and light stabilizers.

The pigments and fillers are usually employed in an amount of 0 to 60%by weight, based on the total weight of the coating agent. The amount ofauxiliaries and additives employed is usually 0.2 to 10% by weight,based on the total weight of the coating agent. The solvent content ofthe coating agent is usually from 30 to 70% by weight, based on thetotal weight of the coating agent. The content of binding agent plushardener is in general 30 to 70% by weight, based on the total weight ofthe coating agent.

The coating agents according to the invention are prepared in a knownmanner by mixing and if appropriate dispersing the individualconstituents.

The coating agents according to the invention are preferably prepared bya process which is characterized in that the acrylate copolymer (A)and/or (B) is prepared by solution polymerization at temperaturesbetween 90° and 160° C., preferably between 110° and 140° C., by

1.) initially introducing at least 10% by weight of the total amount ofthe polysiloxane macromonomer a₁ into the reaction vessel and

2.) metering in the other monomers and any remainder of the polysiloxanemacromonomer a₁ which still exists.

The coating agents according to the invention can be applied in the formof a film to a substrate by spraying, flooding, dipping, rolling,knife-coating or brushing, the film then being hardened to give a firmlyadhering coating.

The coating agents according to the invention are suitable--if lowhardening temperatures of between about 10° C. and 130° C., preferably≦80° C., can be used (see above)--by appropriate choice of the hardenercomponent--for repair painting of motor vehicles and in particular foruse as a top coat and clear coat, but also as a primer and fillermaterial. They are also particularly suitable as a clear coat over abase coat of a metallic multicoat paint.

The invention will be illustrated in more detail in the followingexamples. All the data on parts and percentages are weight data, unlessexpressly stated otherwise.

1. Preparation of Various Acryate Copolymers (A) Containing CarboxylGroups

The acrylate copolymers (A) were in each case prepared in a 4 literhigh-grade steel polymerization kettle with a stirrer, reflux condenser,two monomer feeds and an initiator feed. The particular componentsstated are weighed out and the initial mixture is then heated up to 110°C.

All the feeds are started simultaneously, the two monomer feeds beingmetered in uniformly in the course of 3 hours and the initiator feedbeing metered in over a period of 4 hours. During the polymerization,the temperature in the kettle is kept at 108°-110° C. Thereafter, themixture is subjected to after-polymerization for a further 2 hours. Theacrylate resin solution thus obtained has a solids content of 50%.

The corresponding parts of hexahydrophthalic anhydride (HHPA) are thenadded (see Table), and the addition reaction on the acrylate resin iscarried out at 110° C. When the acid number determination in aqueous andalcoholic KOH gives the same values, the mixture is diluted to a solidscontent of 50% with sec-butanol.

The commercial product Marubeni® AK 5 from Toagosei Chemical IndustriesCo., LTD. was used as the siloxane macromonomer. It has a number-averagemolecular weight of about 5000 and on average one ethylenicallyunsaturated double bond per molecule.

                  TABLE                                                           ______________________________________                                        Example                                                                              A1     A2      A3   A4   A5   A6   A7   A8                             ______________________________________                                        Content                                                                              309.8  178.8   310.3                                                                              310.2                                                                              324.7                                                                              315.5                                                                              313.8                                                                              104.6                          (parts)                                                                       HHPA                                                                          ______________________________________                                        1.1. Preparation of an acrylate copolymer (A.sub.1)  sic!                     Initial mixture:                                                              13      parts of siloxane macromonomer (Marubeni ® AK5)                   552.2   parts of butyl acetate                                                552.2   parts of xylene                                                       Monomer feed A:                                                               130     parts of dimethylaminoethyl methacrylate                              130     parts of ethylhexyl acrylate                                          195     parts of hydroxybutyl acrylate                                        312     parts of n-butyl acrylate                                             Monomer feed B:                                                               208     parts of hexanediol dimethacrylate                                    195     parts of hydroxyethyl methacrylate                                    130     parts of styrene                                                      6.5     parts of mercaptoethanol                                              0.7     parts of triisodecyl phosphite                                        Initiator feed:                                                               65      parts of 2,2'-azobis(2-methylbutanenitrile)                           130     parts of butyl acetate                                                130     parts of xylene                                                       Viscosity (original): >40 dPa s (23° C.)                               Acid number (aqueous/alcoholic): 67.5/71.1 mg of KOH/g                        1.2 Preparation of an acrylate copolymer (A2)                                 Initial mixture:                                                              22.7    parts of siloxane macromonomer (Marubeni ® AK5)                   596.1   parts of butyl acetate                                                596.1   parts of xylene                                                       Monomer feed A:                                                               195     parts of hydroxybutyl acrylate                                        173.3   parts of ethylhexyl acrylate                                          355.3   parts of n-butyl acrylate                                             Monomer feed B:                                                               208     parts of hexanediol dimethacrylate                                    173.3   parts of cyclohexyl methacrylate                                      185.9   parts of hydroxyethyl methacrylate                                    6.5     parts of mercaptoethanol                                              0.65    parts of triisodecyl phosphite                                        Initiator feed:                                                               33.8    parts of 2,2'-azobis(2-methylbutanenitrile)                           67.6    parts of butyl acetate                                                67.6    parts of xylene                                                       Viscosity (original): 3.0 dPa s (23° C.)                               Acid number (aqueous/alcoholic): 75.5/80.4 mg of KOH/g                        1.3 Preparation of an acrylate copolymer (A3)                                 Initial mixture:                                                              596.1   parts of butyl acetate                                                596.1   parts of xylene                                                       Monomer feed A:                                                               65      parts of dimethylaminoethyl methacrylate                              195     parts of hydroxybutyl acrylate                                        162.5   parts of ethylhexyl acrylate                                          312     parts of n-butyl acrylate                                             Monomer feed B:                                                               208     parts of hexanediol dimethacrylate                                    162.5   parts of cyclohexyl methacrylate                                      185.9   parts of hydroxyethyl methacrylate                                    22.8    parts of siloxane macromonomer (Marubeni ® AK5)                   6.5     parts of mercaptoethanol                                              0.7     parts of triisodecyl phosphite                                        Initiator feed:                                                               33.8    parts of 2,2'-azobis(2-methylbutanenitrile)                           67.6    parts of butyl acetate                                                67.6    parts of xylene                                                       Viscosity (original): 11.0 dPa s (23° C.)                              Acid number (aqueous/alcoholic): 74.7/71.2 mg of KOH/g                        1.4 Preparation of an acrylate copolymer (A4)                                 Initial mixture:                                                              596.1   parts of butyl acetate                                                596.1   parts of xylene                                                       Monomer feed A:                                                               195     parts of hydroxybutyl acrylate                                        173.3   parts of ethylhexyl acrylate                                          355.3   parts of n-butyl acrylate                                             Monomer feed B:                                                               208     parts of hexanediol dimethacrylate                                    173.3   parts of cyclohexyl methacrylate                                      185.9   parts of hydroxyethyl methacrylate                                    22.7    parts of slioxane macromonomer (Marubeni ® AK5)                   6.5     parts of mercaptoethanol                                              0.65    parts of trlisodecyl phosphite                                        Initiator feed:                                                               33.8    parts of 2,2'-azobis(2-methylbutanenitrile)                           67.6    parts of butyl acetate                                                67.6    parts of xylene                                                       Viscosity (original): 2.4 dPa s (23° C.)                               Acid number (aqueous/alcoholic): 72.4/70.9 mg of KOH/g                        1.5 Preparation of an acrylate copolymer (A5)                                 Initial mixture:                                                              32.5    parts of siloxane macromonomer (Marubeni ® AK5)                   546.9   parts of butyl acetate                                                546.9   parts of xylene                                                       Monomer feed A:                                                               130     parts of dimethylaminoethyl methacrylate                              195     parts of hydroxybutyl acrylate                                        305.5   parts of n-butyl acrylate                                             130     parts of ethylhexyl acrylate                                          Monomer feed B:                                                               208     parts of hexanediol dimethacrylate                                    195     parts of hydroxyethyl methacrylate                                    123.5   styrene                                                               6.5     parts of mercaptoethanol                                              0.7     parts of triisodecyl phosphite                                        Initiator feed:                                                               65      parts of 2,2'-azobis(2-methylbutanenitrile)                           130     parts of butyl acetate                                                130     parts of xylene                                                       Viscosity (original): thixotropic                                             Acid number (aqueous/alcoholic): 76.8/78.1 mg of KOH/g                        1.6 Preparation of an acrylate copolymer (A6)                                 Initial mixture:                                                              81.3    parts of siloxane macromonomer (Marubeni ® AK5)                   531.9   parts of butyl acetate                                                531.9   parts of xylene                                                       Monomer feed A:                                                               130     parts of dimethylaminoethyl methacrylate                              195     parts of hydroxybutyl acrylate                                        295.8   n-butyl acrylate                                                      130     ethylhexyl acrylate                                                   Monomer feed B:                                                               208     parts of hexanediol dimethacrylate                                    195     parts of hydroxyethyl methacrylate                                    113.5   parts of styrene                                                      6.5     parts of mercaptoethanol                                              0.7     parts of triisodecyl phosphite                                        Initiator feed:                                                               65      parts of 2,2'-azobis(2-methylbutanenitrile)                           130     parts of butyl acetate                                                130     parts of xylene                                                       Viscosity (original): >40 dPa s                                               Acid number (aqueous/alcoholic): 79.1/78.7 mg of KOH/g                        1.7 Preparation of an acrylate copolymer (A7)                                 (Comparison)                                                                  Initial mixture:                                                              162.5   parts of siloxane macromonomer (Marubeni ® AK5)                   503.5   parts of butyl acetate                                                503.5   parts of xylene                                                       Monomer feed A:                                                               130     parts of dimethylaminoethyl methacrylate                              195     parts of hydroxybutyl acrylate                                        279.5   parts of n-butyl acrylate                                             130     parts of ethylhexyl acrylate                                          Monomer feed B:                                                               208     parts of hexanediol dimethacrylate                                    195     parts of hydroxyethyl methacrylate                                    97.5    parts of styrene                                                      6.5     parts of mercaptoethanol                                              0.7     parts of triisodecyl phosphite                                        Initiator feed:                                                               65      parts of 2,2'-azobis (2-methylbutanenitrile)                          130     parts of butyl acetate                                                130     parts of xylene                                                       viscosity (original): >40 dPa s (23° C.)                               Acid number (aqueous/alcoholic): 70.2/69.9 mg of KOH/g                        1.8 Preparation of an acrylate copolymer (A8)                                 (Comparison)                                                                  Initial mixture:                                                              231.9   parts of butyl acetate                                                231.9   parts of xylene                                                       Monomer feed A:                                                               50      parts of dimethylaminoethyl methacrylate                              75      parts of hydroxybutyl acrylate                                        120     parts of n-butyl acrylate                                             50      parts of ethylhexyl acrylate                                          Monomer feed B:                                                               80      parts of hexanediol dimethacrylate                                    75      parts of hydroxyethyl methacrylate                                    50      parts of styrene                                                      2.5     parts of mercaptoethanol                                              0.25    parts of triisodecyl phosphite                                        Initiator feed:                                                               13      parts of 2,2'-azobis(2-methylbutanenitrile)                           26      parts of butyl acetate                                                26      parts of xylene                                                       Viscosity (original): >26 dPa s (23° C.)                               Acid number (aqueous/alcoholic): 75/77 mg of KOH/g                            ______________________________________                                    

2. Preparation of a Polyester Resin

488 parts of hexahydrophthalic anhydride, parts of1,4-cyclohexanedicarboxylic acid, 752 parts of trimethylolpropane, 72.5parts of neopentyl glycol, 82.8 parts of methyldiethanolamine, 200 partsof isononanoic acid, 77 parts of benzoic acid, 88 parts of xylene and1.14 parts of triisodecyl phosphite are introduced into a 4 literpolycondensation kettle with a stirrer, steam-heated column and waterseparator and are slowly heated up. The condensation reaction is carriedout at a temperature of not more than 190° C. to an acid number of 20 mgof KOH/g and a viscosity of 2.0 dPas (50% strength in butyl glycol), andthe mixture is then cooled and partly dissolved with 886 parts of xyleneat 130° C. After further cooling to 50° C., 321.3 parts ofhexahydrophthalic anhydride and 1.12 parts of triisodecyl phosphite arenow added to this solution. The addition reaction of the anhydride iscarried out at not more than 50° C. until an acid number of 68 mg ofKOH/g and a viscosity of 2.4 dPas (50% strength in butyl glycol) arereached. The mixture is then partly dissolved with 377 parts of xyleneand 147 parts of sec-butanol.

The polyester thus obtained has a solids content of 61.5%, an acidnumber of 68 mg of KOH/g and a viscosity of 13.5 dPas (original).

Preparation of a Hardener Solution 1

63.8 parts of a commercially available aliphatic epoxy resin which has amolecular weight of about 1200 and an epoxide equivalent weight of about250-550 and is based on a dinuclear melamine resin, reacted withacrylamide with subsequent epoxidization of the acrylic double bonds(commercial product Monsanto LSE 4114 from Monsanto), and 36.2 parts ofmethoxypropanol are mixed.

Preparation of a Paint Thinner 1

50 parts of methoxypropanol, 25 parts of 1-methoxyprop-2-yl acetate and25 parts of n-butanol are mixed.

EXAMPLES 1 to 6

53 parts of copolymer solutions A1 or A2 or A3 or A4 or A5 or A6, 27parts of polyester resin 1, 1 part of a commercially available lightstabilizer based on benzotriazole (commercial product Tinuvin® 900 fromCiba Geigy), 1 part of a commercially available light stabilizer basedon a sterically hindered amine (commercial product Tinuvin® 440 fromCiba Geigy) and 18 parts of methoxypropanol are stirred successivelyusing a dissolver.

Shortly before application of the clear paint, 50 parts of hardenersolution 1 and 30 parts of paint thinner 1 are admixed. The compositionof the clear paints is summarized in Table 2. The paint mixturesprepared in this way are applied as a clear paint with a dry filmcoating thickness of 50±10 μm by the wet-in-wet process onto acommercially available conventional silver metallic base coat (based onpolyester resin, melamine resin and cellulose acetobutyrate, commercialproduct AE 54 from BASF Lacke+Farben AG; dry film coating thickness 20±5μm).

The coatings thus obtained are tested for drying immediately (dry totouch). For the further tests, all the sheets were first dried at roomtemperature for 1 hour and at 60° C. for 30 minutes. After furtherdrying at room temperature for 24 hours, the pendulum hardness accordingto Konig was determined, the resistance to gasoline was determined withthe aid of the gas spill test and the adhesion was determined with theaid of the taping test. After storage at room temperature for 7 days,the elasticity was determined by means of the cupping index, theresistance to weathering was determined with the aid of the Volvo test,and the scratch resistance of the resulting coatings was determined. Thetests shown in Table 3 were furthermore carried out.

COMPARISON EXAMPLES 1 to 3

The clear paints of Comparison Examples 1 to 3 were prepared, applied,cured and tested analogously to Examples 1 to 6. The clear paint ofComparison Example 1 differs from that of Examples 1 to 6 merely inthat, instead of a copolymer (A) according to the invention, a copolymer(A7) which contains siloxane groups and has too high a content ofpolysiloxane macromonomer a₁ was employed.

The clear paint of Comparison Example 2 differs from that of Examples 1to 6 in that, instead of a copolymer (A) according to the invention, acopolymer (AS) which is free from siloxane groups has now been employed.The addition of 0.01%, based on the total weight of the clear paint,including hardener solution 1 and thinner 1, of a fluorosurfactant as aflow agent furthermore is necessary.

The clear paint of Comparison Example 3 differs from that of Examples 1to 6 in that, instead of a copolymer (A) according to the invention, acopolymer (AS) which is free from siloxane groups has now been employed.0.1%, based on the total weight of the clear paint, of a commerciallyavailable silicone additive (commercial product Tegoglide® 410 fromTegochemie Essen) furthermore was added to the clear paint.

The composition of the clear paints is shown in Table 2. The testresults on the coatings are summarized in Table 4.

                  TABLE 1                                                         ______________________________________                                        Composition (in % by weight) and parameters of copolymers A1 to A8                   A1   A2     A3     A4   A5   A6   A7   A8                              ______________________________________                                        Dimethyl-                                                                              10.0   --     5.0  --   10.0 10.0 10.0 10.0                          aminoethyl                                                                    methacrylate                                                                  Ethylhexyl                                                                             10.0   13.3   12.5 13.3 10.0 10.0 10.0 10.0                          acrylate                                                                      Hydroxybutyl                                                                           14.9   15.0   15.0 15.0 15.0 15.0 15.0 15.0                          acrylate                                                                      n-Butyl  23.9   27.4   24.0 27.4 23.5 22.75                                                                              21.5 24.0                          acrylate                                                                      Hexanediol                                                                             15.9   16.0   16.0 16.0 16.0 16.0 16.0 16.0                          dimethacrylate                                                                Hydroxyethyl                                                                           14.9   14.3   14.3 14.3 15.0 15.0 15.0 15.0                          methacrylate                                                                  Styrene  10.0   --     --   --   9.5  8.75 7.5  10.0                          Cyclohexyl                                                                             --     13.3   12.5 13.3 --   --   --   --                            methacrylate                                                                  Siloxane 0.4    0.7    0.7  0.7  1.0  2.5  5    --                            macromonomer                                                                  OH number                                                                              115.3  114.2  115.1                                                                              115.1                                                                              115.3                                                                              115.3                                                                              115.3                                                                              119.8                         (intermediate                                                                 product) (mg                                                                  of KOH/g)                                                                     OH number                                                                              27.3   22.2   25.3 25.2 23.6 25.9 26.0 39.4                          (end) (mg of                                                                  KOH/g)                                                                        Acid number                                                                            67.5   75.5   74.7 72.4 79.1 76.8 70.2 70.0                          (end) (mg of                                                                  KOH/g)                                                                        Acid number                                                                            71.1   80.4   71.2 70.9 78.7 78.1 69.9 70.4                          (end) (mg of                                                                  KOH/g)                                                                        Amine number                                                                           28.5   --     14.0 --   27.6 27.9 27.8 27.6                          (end) (mg of                                                                  KOH/g)                                                                        Siloxane in                                                                            i.m.   i.m.   feed feed i.m. i.m. i.m. --                            ______________________________________                                         i.m. = initial mixture                                                   

                  TABLE 2                                                         ______________________________________                                        Clear paint compositions in parts                                             Example  1      2     3    4   5    6   V1   V2   V3                          ______________________________________                                        Copolym A1                                                                             53                                                                   Copolym A3      53                                                            Copolym A3            53                                                      Copolym A4                 53                                                 Copolym A5                     53                                             Copolym A6                          53                                        Copolym A7                              53                                    Copolym A8                                   53   53                          Polyester                                                                              27     27    27   27  27   27  27   27   27                          Tinuvin ® 900                                                                      1      1     1    1   1    1   1    1    1                           Tinuvin ® 440                                                                      1      1     1    1   1    1   1    1    1                           Methoxy- 18     18    18   18  18   18  18   17.99                                                                              17.9                        propanol                                                                      Fluoro   --     --    --   --  --   --  --   0.01 --                          surfactant                                                                    Silicone --     --    --   --  --   --  --   --   0.1                         Hardener 50     50    50   50  50   50  50   50   50                          solution 1                                                                    Thinner 1                                                                              30     30    30   30  30   30  30   30   30                          ______________________________________                                    

All the clear paints were formulated with thinner 1 to spray viscosityof a flow time of 18-20 seconds in a DIN 4 cup at 23° C. The solidscontent of the clear paints at the spray viscosity was 40-45%.

                  TABLE 3                                                         ______________________________________                                        Test results                                                                  Example 1       2       3     4     5     6                                   ______________________________________                                        Pendulum                                                                              76      67      63    60    70    75                                  hardness                                                                      (s).sup.1)                                                                    Dry to touch                                                                          20      30      60    75    20    20                                  (minutes)                                                                     Taping test.sup.2)                                                                    3       3       1     0     3     3                                   Gas spill                                                                             10      10      10    10    10    10                                  test.sup.3)                                                                   Gas spill test                                                                        9       9       --.sup.9)                                                                           --.sup.9)                                                                           9     10                                  10 cycles                                                                     Volvo                                                                         Cupping 6       6       6     5     6     6                                   index (mm)                                                                    Volvo test.sup.4)                                                                     m3 g1   m4 g1   m5 g2 m5 g3 m2 g1 m1 g1                               10 cycles                                                                             g.l.s.  l.s.    s.s.  s.s.  g.l.s.                                                                              g.l.s.                              Scratch l.m.    m.      m.    s.m.  l.m.  l.m.                                resistance.sup.5)                                                             Wetting >90     >90     >90   >90   >90   >90                                 angle.sup.6 (°)                                                        Capacity for                                                                          OK      OK      NOK   NOK   OK    OK                                  over-                                                                         painting.sup.7)                                                               Flow    OK      OK      NOK   NOK   OK    s.i..sup.10)                        DOI.sup.8)                                                                            93      94      90    90    93    94                                  Clouding                                                                              none    none    slight                                                                              slight                                                                              slight.sup.11)                                                                      severe.sup.12)                      ______________________________________                                         .sup.9) No longer assessable, impaired surface                                .sup.10) Flow slightly impaired                                               .sup.11) Clouding disappears after stirring                                   .sup.12) Clouding becomes less after stirring                            

                  TABLE 4                                                         ______________________________________                                        Test results                                                                  Example          V1       V2      V3                                          ______________________________________                                        Pendulum hardness (s).sup.1)                                                                   --.sup.9)                                                                              71      70                                          Dry to touch (minutes)                                                                         --       45      45                                          Taping test.sup.2)                                                                             --       1       1                                           Gas spill test.sup.3)                                                                          --       5       5                                           Gas spill test 10 cycles Volvo                                                                 4        5                                                   Cupping index (mm)                                                                             --       4.5     5                                           Volvo test.sup.4)                                                                              --       m5 g3   m5 g3                                       10 cycles        --       s.s.    s.s.                                        Scratch resistance.sup.5)                                                                      s.m.     m.                                                  wetting angle.sup.6) (°)                                                                --       75-85   80-90                                       Capacity for overpainting.sup.7)                                                               --       NOK     OK                                          Flow             --       OK      OK                                          DOI.sup.8)       --       81      82                                          Clouding         --       none    none                                        ______________________________________                                         Explanations on Table 3 and Table 4:                                          .sup.1) Pendulem hardness according to Konig in seconds                       .sup.2) Tesakrepp ® 4330 is stuck on the film and removed after 1         hour. The marking is evaluated visually: 3 = no marking, 2 = light            marking, 1 = marking, 0 = sever marking                                       .sup.3) 5 ml of comercially available supergrade gasoline are introduced      onto the solid  sic! sheet placed at an angle of 45°. After 5          minutes, the marking is evaluated: 1 = very severe marking, 10 = no           marking. This test is carried out sheets which have been dried for 1 hour     at room temperature, 30 minutes at 60° C. and 24 hours at room         temperature. This test is furthermore repeated on sheets which have benn      exposed to 10 stress cycles in the Volvo test.                                .sup.4) The test sheets are exposed to 10 stress cycles, one cycle being      composed as follows: 4 hours of storage at 50° C., followed by 2       hours of storage at 35° C. and 100% relative atmospheric humidity,     followed by 2 hours of storage at 35° C., 100% relative atmospheri     humidity and 2 l of So.sub.2  sic! per 300 l of air and finally 16 hours      of storage at -30° C. The degree of blistering is then evaluated       according to DIN 53 209 and  sic!: g.l.s. = gloss lightly swollen, l.a. =     lightly swollen, s.s. = severly swollen.                                      .sup.5) 250 g of sea sand were poured from a height of 1 m onto a test        sheet, placed at an angle or 45°, over an area of 5 × 5 cm.      The marking is then evaluated: l.m. lightly marked, m = marked, s.m. =        severely marked.                                                              .sup.6) The wetting angle was measured using a drop of water.                 .sup.7) The test sheets were dried at room temperature for 1 hour, at         60° C. for 30' and at room temperature (RT) for 24 h. The upper        half of the test sheets was then sanded, dry, with 600 grade emery paper.     The left half (sanded and nonsanded part) was then oversprayed with a         commercially available conventional base paint based on polyester resin,      melamine resin and cellulose acetobutyrate (AE 54 from BASF Lacke + Farbe     AG, Munster). The entire test sheet was then coated with the particular       cleat paint (dry film layer thickness 50-60 μm). The sheet was then        dried at 60° C. for 30 minutes. The coating was subsequently           evaluated visually: OK = no swelling is to be observed in any region.         .sup.8) Measured using a 1792 unit from ATI Systems Inc., 32355 Howard        Ave. Madison Heights, Michigan, USA                                           .sup.9) The clear paint of Comparison Example 1 is very severly clouded.      On spraying, severely impaired surfaces are obtained. Therefore no furthe     tests were carried out.                                                  

Summary of the Test Results

Comparison of Examples 1 to 6 with Comparison Examples 1 to 3 shows thatthe resistance of the resulting coatings to gasoline is improvedsignificantly by the incorporation of small amounts of the polysiloxanemacromonomer a₁. The resistance of the resulting coatings to gasolineafter stress (10 cycles in the Volvo test) is also improvedsignificantly. The scratch resistance and surface smoothness of theresulting coating furthermore are also improved significantly.

Comparison of Example 1 with Comparison Example 2 moreover shows thatthe capacity of the resulting coatings for being overpainted is alreadyachieved after storage at room temperature for 24 hours by theincorporation of small amounts of the polysiloxane macromonomer a₁, andthat the top coat appearance is improved and that the short-termweathering results in the Volvo test are improved from an unacceptablelevel to an acceptable level.

Comparison of Examples 2 and 4 and of Examples 5 and 6 furthermore showsthat the polysiloxane macromonomer a₁ is advantageously initiallyintroduced into the reaction vessel in the preparation of copolymer A,but that acceptable results are also obtained if the polysiloxanemacromonomer a₁ is metered in with the other monomers.

We claim:
 1. A coating agent which comprises, as the binding agent, atleast one polymer containing carboxyl groups and, as the hardener, atleast one epoxy resin having on average more than one epoxide group permolecule, wherein: the binding agent comprises at least one acrylatecopolymer (A) which comprises carboxyl groups and is prepared bysolution polymerization using from 0.4 to 2.5% by weight, based on thetotal weight of the monomers, of one or more polysiloxane macromonomersa₁ having a number average molecular weight of 1000 to 40,000 and onaverage 0.5 to 2.5 ethylenically unsaturated double bonds per molecule,wherein copolymer A has a number average molecular weight of between5000 and 25,000.
 2. The coating agent according to claim 1, wherein theacrylate copolymer (A) is prepared using from 0.4 to 1% by weight, basedon the total weight of the monomers, of one or more polysiloxanemacromonomers A₁.
 3. A coating agent according to claim 1, wherein theacrylate copolymer (A) is prepared using one or more polysiloxanemacromonomers a₁ which is prepared by reaction of 70 to 99.999 mol % ofa compound (1), represented by the formula (I) ##STR7## in which R₁represents an aliphatic hydrocarbon group with 1 to 8 C atoms or aphenyl radical and R₂, R₃ and R₄ in each case represent a halogenradical or an alkoxy radical having 1 to 4 C atoms or a hydroxyl group,with 30 to 0.001 mol % of a compound (2), represented by the formula(II) ##STR8## in which R₅ represents a hydrogen atom or a methylradical, R₆, R₇ and R₈ in each case represent halogen, OH or an alkoxyradical having 1 to 4 C atoms or an aliphatic hydrocarbon group having 1to 8 C atoms, at least one of the radicals R₆, R₇ or R₈ being halogen,OH or an alkoxy group, and n represents an integer from 1 to
 6. 4. Acoating agent according to claim 1, wherein the acrylate copolymer (A)is prepared using one or more polysiloxane macromonomers a₁ having theformula ##STR9## wherein R₁ =H or CH₃ R₂, R₃, R₄ and R₅ =identical ordifferent aliphatic hydrocarbon radicals having 1 to 8 C atoms, inparticular or the phenyl radical, n=2 to 5, and m=8 to
 30. 5. A coatingagent according to claim 4, wherein, in the formula for the polysiloxanemacromonomers a₁, R₂, R₃, R₄ and R₅ =identical or different aliphatichydrocarbon radicals selected from the group consisting of the methyland phenyl radicals, and n=3.
 6. A coating agent according to claim 1,wherein the acrylate copolymer (A) containing carboxyl groups isprepared by copolymerization ofa₁) 0.05 to 2.5% by weight, of one ormore polysiloxane macromonomers a₁, a₂) 0 to 40% by weight, of one ormore ethylenically unsaturated monomers containing carboxyl groups, a₃)0 to 40% by weight, of one or more vinylaromatic hydrocarbons, a₄) 0 to99.95% by weight, of one or more ethylenically unsaturated monomerscontaining hydroxyl groups, a₅) 0 to 30% by weight, of one or moremonomers having at least two polymerizable, ethylenically unsaturateddouble bonds and a₆) 0 to 80% by weight of one or more otherethylenically unsaturated copolymerizable monomers, wherein the sum ofthe parts by weight of components a₁ to a₆ is in each case 100% byweight and wherein the amounts of components a₂ and a₄ employed shouldnot both simultaneously be zero, and when component a₄ is present, thecopolymer obtained therewith is reacted with a carboxylic acid anhydridein an amount sufficient to produce a copolymer with an acid number offrom 40 to 150 mg of KOH/g.
 7. A coating agent according to claim 1,wherein the acrylate copolymer (A) containing carboxyl groups isprepared by copolymerization ofa₁) 0.05 to 0.5% by weight, of one ormore polysiloxane macromonomers a₁, a₂) 0 to 30% by weight, of one ormore ethylenically unsaturated monomers containing carboxyl groups, a₃)0 to 30% by weight, of one or more vinylaromatic hydrocarbons, a₄) 20 to60% by weight, of one or more ethylenically unsaturated monomerscontaining hydroxyl groups, a₅) 0 to 20% by weight, of one or moremonomers having at least two polymerizable, ethylenically unsaturateddouble bonds and a₆) 0 to 80% by weight of one or more otherethylenically unsaturated copolymerizable monomers, wherein the sum ofthe parts by weight of components a₁ to a₆ is in each case 100% byweight, and wherein the amounts of components a₂ and a₄ employed shouldnot both simultaneously be zero, and when component a₄ is present, thecopolymer obtained therewith is reacted with a carboxylic acid anhydridein an amount sufficient to produce a copolymer with an acid number offrom 40 to 150 mg of KOH/g.
 8. A coating agent according to claim 1,wherein the hardener, is selected from the group consisting of polarepoxides based on a reaction product of melamine resins with acrylamidewith subsequent epoxidation of the acrylic double bond.
 9. A process forthe preparation of the coating agent according to claim 1, comprisingthe steps of mixing the acrylate copolymer(s) (A) and the epoxy resin(s)with one or more organic solvents to form a first mixture, and thenoptionally dispersing in the first mixture at least one member selectedfrom the group consisting of pigments, fillers and further additivesother than fillers.
 10. A process according to claim 9, whereincharacterized in that the acrylate copolymer (A) containing carboxylgroups is prepared by solution polymerization at temperatures of between90° and 160° C. using one or more polymerization initiators, by1.)initially introducing at least 10% by weight of the total amount of thepolysiloxane macromonomer a₁ into the reaction vessel and 2.) meteringin the other components and any remainder of the polysiloxanemacromonomer a₁ which still exists.
 11. The process according to claim10, wherein 100% by weight of the total amount of the polysiloxanemacromonomer and optionally at least 60% by weight of the total amountof a vinyl ester of aliphatic monocarboxylic acids which are branched inthe α-position and have 5 to 15 C atoms per molecule are initiallyintroduced into the reaction vessel.
 12. A process for coatingsubstrates, wherein a coating agent according to claim 1 is applied. 13.The coating agents according to claim 1, comprising an automotive repaircoating composition.
 14. The coating agents according to claim 1,comprising a clear coat composition.
 15. The coating agents according toclaim 1, comprising a clear coat composition for multilayer metallicpainting.
 16. The coating agents according to claim 1, comprising a topcoat coating composition.
 17. The coating composition of claim 1,wherein the epoxy resin is an acrylate copolymer which comprises epoxidegroups and is prepared by solution polymerization using between 0.05 and2.5% by weight, based on the total weight of the monomers employed forthe preparation of copolymer, of one or more polysiloxane macromonomersa₁ having a number-average molecular weight of 1000 to 40,000 and onaverage 0.5 to 2.5 ethylenically unsaturated double bonds per molecule,and having a number average molecular weight of between 800 and 2200 andan epoxide equivalent weight of between 250 and
 550. 18. A coating agentaccording to claim 17, wherein characterized in that the acrylatecopolymer comprising epoxide groups is prepared using one or morepolysiloxane macromonomers a₁ which is prepared by reaction of 70 to99.999 mol % of a compound (1), represented by the formula (I) ##STR10##in which R₁ represents an aliphatic hydrocarbon group with 1 to 8 Catoms or a phenyl radical and R₂, R₃ and R₄ in each case represent ahalogen radical or an alkoxy radical having 1 to 4 C atoms or a hydroxylgroup, with 30 to 0.001 mol % of a compound (2), represented by theformula (II). ##STR11## in which R₅ represents a hydrogen atom or amethyl radical, R₆, R₇ and R₈ in each case represent halogen, OH or analkoxy radical having 1 to 4 C atoms or an aliphatic hydrocarbon grouphaving 1 to 8 C atoms, at least one of the radicals R₆, R₇ or R₈ beinghalogen, OH or an alkoxy group, and n represents an integer from 1 to 6.19. A coating agent according to claim 17, wherein characterized in thatthe acrylate copolymer comprising epoxide groups is prepared using oneor more polysiloxane macromonomers a₁ having the formula ##STR12## whereR₁ =H or CH₃ R₂, R₃, R₄ and R₅ =identical or different aliphatichydrocarbon radicals having 1 to 8 C atoms, or the phenyl radical n=2 to5, m=8 to
 30. 20. A coating agent according to claim 1, wherein furthercharacterized in that at least one copolymer (A) is prepared by solutionpolymerization using from 0.4 to less than 1.0% by weight, based on thetotal weight of monomers employed for the preparation of copolymer (A),of one or more polysiloxane macromonomers a₁.